Automatic telephone exchange



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ATTORNEY wanted, to place him in communication with Patented Oct. 13, 1925.

UNITED STATES,

PATENT orrlcs.

ALEXANDER E. KEITH, JOHN ERICKSON, AND CHARLES J. ERICKSON, OF CHICAGO, ILLINOIS, ASSIGNORS, BY MESNE ASSIGNMENTS, TO AUTOMATIC ELECTRIC COM- IANY A CORPORATION OF ILLINOIS.

Application filed June 18,

To all whom it may concern:

Be it known that we, ALEXANDER E. KEITH, J OIIN ERICKSON, and CHARLES J. ERIoKsoN, all citizens of the United States, residing at 'Chicago, in the county of Cook and State of Illinois, have invented new and useful Automatic Telephone Exchanges, of which the following is a specification. Our invention relates to automatic telephone exchanges, and our object is to provide a new system of mechanism adapted to use in large exchanges of say ten thousand or more subscribers without introducing undue complication of either the switch mechanism or interconnecting wires. In Letters Patent of the United States for automatic telephone exchanges, granted to us December 5, 1899, and numbered 638,249, 1n connection with Letters Patent of the United States for calling devices for automatic telephone exchanges granted to us January-11, 1898, and numbered 597,062, is embodied a systemof automatic telephone exchange whiEh in practice consists of a comb nation oi the calling device at the subscribers station and the exchange mechanism at the central station. The calling device consists of a pivotally mounted disk havingat one side marginal edge, ten holes numbered consecutively from 1 to 9 and 0, and is operated to call a certain number by'ins'erting a finger in a hole designated by the proper numeral and turning the disk until the finger contacts a stop and is then released, after which, by virtue cf'aspring the disk isreturned vthe first position, and this return movenient through proper step by step mech-- anism, causes electric currents alternately over two line wires to. operate the proper magnets at the central exc ange, and set the subscribers switch to. the contact point another subscriber.

In the above described system the selector or subscribers switch for a-system of one hundred subscribers has one hundred contact points disposed in ten concave rows of ten in each row, and each of these contact points is adapted to be engaged by a switch arm mounted on a shaft which is fitted to mo e step by step both vertically and ina rotary direction.

In automatic telephone exchanges of. the

18 02. Serial No. 112,224.

the banks of each switch or selector are directly connected by interconnecting or bank ings and specification, herewith, and which" is adapted to exchan es of ten thousand or more subscribers, alt ough the calling devices and the general principles involved inthe construction'of the switches are similar -to those embodied in the invention shown in the patents hereinbefore referred to, yet

several important new devices adapted to perform new functions have been added, and the electrical connectionsof the switches are such that the latter are arranged relatively in several groups of whicl1,"in the first group there is one switch for each subscriber, the switches in this group being termed first selectors. The switches in the second group are termed second selectors,

and in number are usually not more than ten er cent of the number of switches in the rst group.

The switches in the third group are termed connectors, and are usually less in number than the number of switches in the first named' group, and may be equal in number .tothe number of'swit'ches in the secondnamed group. I J

The several groups of both selectors and connectors may each be subdivided into secondary groups or sections as may be desired.

In this newsystem, the first electrical impulses caused by the calling device, instead of first connecting vdirectly to the subscribers line, automatically connect the calling subscribers line to some one of ten or more trunk lines which lead to groups of switch instruments or second. selectors, which are in turn connected with another group of switch instruments or connectors, which" latter operate to connect with the son ht for subscriber so that, in an exchange or one hundred to nine hundred and ninety-nine subscribers, the first electrical impulses sent in by the calling device will pick out some one of the trunk-lines leading to a group of selector switches numbered for the first digit of the number of subscriber sought, and the next electrical impulses select from this group the contact point representing the last two digits of the subscribers number sought, but in exchanges of this kind arranged for a still larger number of subscribers than last above mentioned, say for from one to ten thousand subscribers, as is embodied in the present invention, the electrical impulsescaused by the calling device, automatically pick out first, the thousand gro'u of second selectors and then, the un reds'group of connectors in which the called number is found.

Sinoeseveral kinds of calling devices may be used to control electric currents at the propertime, and .over the proper line, automatically, and since such constructions and their operation are somewhat intricate, and would unnecessarily complicate this case, we

have substituted therefor simple calling keys by which the action of the proper mechanism at the proper time may be fully and easily illustrated.

The automatic calling device particularly adapted to control the electric currents for this new system is the subject of a separate application for patent. I he principalobjectof our invention is to'provide practical means whereby from any of the secondary groups or sections of the subscribers or first selectors the proper interconnecting of trunk lines leading to any other desired 'first selector in the same or any other group of first selectors, may be automatically and very quickly selected, and

thereby connect any two distant subscribers whose lines are not engaged, the operation of calling another subscriber being such that should several of the trunk lines he in use, the first and second selectors would, so to speak, automatically pass over these busy trunk lines and select the first idle trunk line through which communication could be established, all of which is more fully described hereinafter, and illustrated in the accompanying drawing in which:

Fig. 1, is a front elevation of one of either the first or second selectors, and Fig. 2, is a side elevation of the same looking in the direction indicated by arrow A, Fig. 1.

Fig. 3,.is an elevation of the opposite side shown in Fig. 2, but with the parts below the main frame removed.

Fig. 4, is a plan of'what is shown in Fig. 3.

Fig.5, is a cross section on broken lines B, C, Fig. 3, to illustrate the normal position of several of the operative parts.

Fig. 6, is a cross section, same as the outer portion of Fig. 5, to illustrate. the main tent in the position it is made to assume when the switch shafts longitudinal motion detent is in the engaged position shown in Fig. 6.

Fig. 9, is the same as Fig. 8, but with the rotary detent in engagement with the first tooth of the main switch shafts rotary ratchet, and showing the inward or operated position of the arm through which the auxiliary switch is moved to the normal position by virtue of the release armature spring Fig. 10, is a cross section on broken line F, G, Fig. 3, showing the auxiliary switch mechanism in the normal position, with several important parts in broken lines.

Fig. 10 is a perspective view of the auxiliary switch contact points, as they appear embedded in a bracket of insulating material shown in end elevation in Fig. 10, attached to the side of the main frame.

Fig. 11, is the same section as Fig. 10, but with the parts in the operatedposition.

Figs. 5 to 11, inclusive, except Fig. 10, are sections on the broken lines stated, look- ;Fng in the direction indicated by arrow H,

Figs. 12, 13, 14: and 15 are partial side elevations of an auxiliary switch release and a cut-out mechanism, to illustrate different positions of the operative parts.

Fig. 16, is a side elevation of one corner portion of what is shown in Fig. 2, but with several parts removed, to illustrate the means for permitting the main switch shafts ratchet detents to be brought into engagement with ratchet wheelteeth on this switch shaft, by the disengagement of a re lease lock spring.

Fig. 17, is a side elevation of a detached portion of what is shown in Fig. 16,.and-

tive mechanism in connection therewith, the

same as shown at the top of Fig. 2, but on an enlarged scale, with the operative parts in several different positions, as when in use.

Fig. 23, is an elevation of a pair of retardation magnets, same as shown mounted at the rear of the relay magnets in Fig. 2, but on same scale as Fig. 20, the operative parts being in the normal position.

Fig. 24, is a side elevation of a portion of the principal operative parts in the normal position, of a connector which is used for all the groups of Connectors, and which differs in several minor parts from the se= lectorsillustrated inthe preceding figures.

Fig. 24, also shows an electromagnet secured at the lower end of the frame, which serves as a means for operating a spring switch, whose parts are normally in the talking circuit, but which circuit may be cut out, and the party he placed in the signal circuit.

Fig. 25, is the same as a portion of Fig. 24, but showing several of the parts of the connectors in the operated position.

Figs. 26 and 27, are cross sections'on broken line I, J, Fig. 24, to illustrate, respectively, the normal and the operated position of mechanism ada ted to 1ock,,at normal position, the auxiliary switch of the connectors.

. Fig. 28, is a detail sketch, to illustrate means for imparting movement to unlock the auxiliary switch of the connectors.

Fig. 29, is a plan of a circuit breaker operated by an electric motor, and showing diagrammatically the battery connections.

Figs. 30 and 30, show, respectively, a side and an end elevation of a three part commutator fora circuitbreaker, and Figs. 31 and 31, a side and an end elevation of a piece of tubular insulation serving to insulate the parts shown in Fig. 30, from the shaft of the rotary circuit breaker of Fig. 29.

Fig. 32, is a side elevation of the commu tator of a single circuit breaker, whichis shown in position in Fig. 29.

Figs. 33 and 34L are connected diagrammatic illustrations, to indicate the general system of electrical connections from one subscriber to another, and the course of the signalling-and talking circuit, together with battery connections direct and through the circuit breaker, the induction and retarda tion coils and the relay magnets, of which illustrations, in Fig. 33, there are three sections indicated by the letters A, B and C, and in Fig.34, there are four sections, indicated by letters D, E, F and G, of which sections A, B and C, of Fig. 33, A. shows a telephone receiver, hook, signal magnets. and two ordinary signal keys, to re resent a subscribers calling station; while and C, respectively, represent a first and a second selector.

In these figures the resistances and the retardation coils are shown by their conventional formsbut'in Fig. 47, circles are used to designate them.

In Fig. 34, sections D and E, respectively,

represent a connector and a first selector, through which connection is made. to the called subscribers station at section F, which is a duplication of station A, while section G, is the central station battery and connections, together with devices for delivering electric currents througha series of wires of which latter, four are also seen in .Fig. 33, and referred to hereinafter.

after fully described, how, through the ac tion of any subscribers selector, the trunk lines are automatically selected, the automatic mechanism being capable of passing all engaged trunk lines but certain to make connection with the first one not in use.

In Fig. 37, the single curved row of contact points are indicated, together with the -main switch shaft, and a switch arm for each selector and connector of'what we term the private banks, and also the complete circuits for said banks including the auxiliary switch arms therefor and the main battery. In Fig. 47, double curved rows of contact points are indicated, in what we term the connecting banks of contact points, both the private and connecting banks being simply indicated in Figs. 1 and 2, at tached to the lower portion of both the selectors and connectors. In other words, the two figures are virtually horizontal sections through the shaft and contact making mechanism in two planes, 37 being through the private bank or the bank by meansof which connections are made to prevent interference after a talking circuit has been estab- I lished and 47 through the connecting bank by means of which a talking circuit is established. The particular construction to prevent cross talk. is fully illustrated in Figs. 38 to 45, inclusive, in which Fig.-

.ends of the closely adjacent row are disposed in proper position in plan view, arranged in pairs, of which, each contact point is insulated from all the others and each is adapted to be contacted by one member of the dduble main switch arms, which latter are insulated one from the other, and from the main switch shaft; as illustrated in Fig. 39, where is shown a side elevation of a portion of the main switch shaft, with a single contact point knife switch arm insulatingly mounted thereon, and in contact with the usual single contact points of the private banks; and there is also the double switch arm in contact with the double contact points of the connecting banks, the banks both being shown-in section, to partially illustrate the comparative difference in arrangement of the private and connecting banks, which latter are illustrated in 'de=- Q tail in Figs. 40 to 45, inclusive, in which,

Figs. 40 and 41 are, respectively, a plan and a front elevation of a bank of only five rows.

of double contact. points which will serve to fully illustrate the construction of full banks of ten double rows of contact points.

Fig. 12 is a front elevation of one of the sections comprising a row of double contact points in Fig. 11.

Fig. 43 is a front elevation of one condenser plate section, which is disposed between adjacent double rows of contact points,-for the purpose of preventing cross talk, as is hereinafter explained.

Fig. 44 is a cross section, on broken line K, L, Fig. 40, to clearly illustrate the component'parts of the bank: 4.;

Fig. 45 is a perspective v y ,of a metal comb shaped piece for making electrical connection between all the metal condenser plates of the bank, the same being shqwn in position in Fig. 41 at each side portion of the drawing. if 3 Fig. 46, illustrates, diagrammatically, three connectors, of which, twojare in sec tion H, and one in section I, and also illustrates the private bank wires and battery connections, for the purpose of showing the difference between a busy connector or line, a connector at normal, and a third connectot-.' seeking to make a connection with a busy line.

Similar numerals indicate like parts throughout the'several views, and since in both the selectors and connectors most of the important parts may be. and are, in this instance, substantially alike, they are designated, when alike, by the same numerals, the parts, however, which are not common in the selectorsand connectors are hereinafter designated by separate numerals, and the differences, both in construction and function particularly. designated; and since ,many of the principal operative parts of shaft being limited at its normal position by not consist so much in the particular mechanical movements em loyed, as in other features hereinbefore re erred to, and hereinafter fully described.

The frames 10f both the selectors and connectors are the same, and there is, in common, a vertically disposed step by step sliding, rotative main switch shaft 2, mounted on the frame, and this shaft is provided with switch arms 3, l -"and 5, which, by virtue of the step by step sliding, rotative motion of the shaft,are ada ted to contact any one oftwo banks 6 and of contact points, which are arranged in concave rows, Fig. 1. The step 'by' step rotative motion is imparted to the main switch shaft 2 by virtue of "electromagnet 8, which operates long ,ratchet wheel 9 through lever 10 and pawl 11 k The step by step longitudinal movement of shaft 2 is accomplished by the action of vertical electromagnet 12, which operates cylindrical ratchet 13 through vertical magnet lever 14 and pawl 15.

Shaft 2, issuccessively lifted step by step against gravity, and is rotated against the resiliency of a spring 16 connecting the lower end with the frame, as shown, in Figs. 1 and 2, the downward movement of the '5 a collar 17, or any other suitable device contacting the frame, and the normal rotar position is maintained by a pin 18 whic contacts a pin 19 projecting from the top of the frame.

A small short pin 20, Figs. 1 and 2,'in the. top of the frame will be contacted by pin 18 and hold the shaft in the initial position,- if van effort is made to rotate it, until after one vertical step movement is completed.

There is a double detent having one arm 21 adapted to engage the circular teeth of the cylindrical ratchet 13, and'another arm 22 for engaging the teeth of ratchet wheel 9, the two detent-s being yieldingly held in 1211- 110 gagement with the ratchets by spring 23.

Shaft 2, as in the previous inventions hereinbefore referred to, is provided with means which prevents any further vertical movement after the shaft has been rotated one step, and comprises a stationary detent 24 whlch is secured to frame 1, Figs. 1, 3, 4, 5 and 6, and the point thereof is in a groove 25, which is longitudinal of cylinder ratchet 13, and plainly shown in Fig. 3, and in cross sections of the ratchet in Figs. 5- and 6.

The point of stationary detent 24 will remain in groove. 25 so long as shaft 2 is only moved step by step vertically, but if it is moved but one rotative step, the point of the detent engages in a groove between two teeth of the cylinder ratchet 13, and although it permits the shaft to rotate farther, now prevents any longitudinal or vertical movement either way, thus effectually pre- 3 contact points 33-, 34, 35, 36 and 37, Figs. 1,

venting the switch arms 3, and 5 from being bent or injured, when they are once in engagement with any of the concave rows of conment must first be made to the particular row wanted, and when the particular contact point is found in the row, the operation of the release must first cause the shaft to reverse its motion in a rotary direction, so

that the switch arms 3, 4 and 5 are clear of the contact points, and detent 24 is in groove 25, before shaft 2 falls to the initial position shown in Figs. 1 and 2.

and connectors,- in this instance, comprises five switch arms 26, 27,28, 29 and 30, which are insulatinglv secured at one end to an arm 31 secured to shaft 32, which latter is revolubly mounted at the ends in frame 1. u

The switch arms 26' to 30, inclusive, are normally in engagement with five insulated 3, 10, 10 and 1-1, but are adapted by a movement ,caused byspring 38 oir shaft 32 to be disengaged. from these points, and be placed in connectionfwit'hfiye other insulated contact points: 39 40, 41, 42- and 4 3.

This far, *the'selectors and connectors are alike, but the five auxiliary switch arms of both. the first and second selectors are not held by the same means in engagement with the contacts33 to 37, inclusive, 1n the normal position, nor are they caused to be disengaged to engage contacts 39 to 43, inclusive, by the same means as in the connectors, and this constitutes the real difference in the construction between the connectors and selectors, with the exception of the ringing. magnet attached to the connector switclng, -Fig. 24.

In the selectors, the five switch arms are held in engagement in the normal position shown in Figs. 1, 2, 3, and particularly Fig. 10, with the outer row of contact points 33,

. 34, 35, 36 and 37 by means of an arm.44

which forms a bell crank lever with arm-31, and extends across switch frame 1, and the outer end portion ofthis arm is adapted to be engaged by a shoulder 45 at the top of a spring arm 46 extending from the armature 47 of a magnet 48, for controlling the auxiliary switch, and may alsobe engaged by second shoulder 49 at the top end of a rigid arm 50, which also extends from armature The shoulder 45 of spring arm 46 is disposed at a less distance outwardly than shoulder 49 of arm 50, as is plainly shown in Fig. 2, and especially in Figs. 12 to 15, inclusive, so "that the shoulders of these arms do not register for the purpose as is hereinafter fully explained in describing the operation of the auxiliary switch.

is pivotally secured'the end of a bent connecting rod 51 which extends across to the opposite side of the main frame, where its slotted or bifurcated end is'in engagement with an arm 52 of the double detent 21. g 53 is the release electro-m'agnet, whose armature'54 is pivotally attached atone end to'frame 1,- and is heldout of contact with" the magnet. by means of a comparatively strong spring '55. 4 '1 The auxiliary switch, in both the selectors at the outer end of this spring is a hole 57 58 from double detent 21;.

T disposed so: as to engage with; a projection;

Projectin from :magnet lever-sl4'fiFigs. 24 and. 25,5,sa hook59 adapted to contact the under side of spring 56 and disengage-1 the springfro'rn the projection 58; of double detent- 21,- when lever 14 is operated the first time from the normal position.

In the connectors, Figs. 24 and 25, is shown the auxiliary switch magnet 48, but instead of the switch spring 62 and 63 being attached thereto, as. in the selector, there'is attached acatch spring having a shoulder at the top ,end similar .to hook spring 46, Figs. 2 and 12, of the selectors, anda rigid armature arm 71, havin a bent outer end portion which contacts t e catch spring as shown. 1

The connectors, Fig. 24, also differ from the selectors because armature 69 of magnet 48 is always closed in the initial position, whether the armature of rotary magnet 8 is closed or not, and armature 69 is held in the closed position during the time and for the purpose hereinafter explained.

In the connector, Fig. 24, lever 44 is seen in engagement with'the shoulder near the outer end of catch spring 70, when the parts are in the normal position.

Also, the connectors differ from the selectors in that each of them is provided with a yielding controller comprising a rod pivotally connected at one end to the lrigid armature arm, 71, the other end of this rod being connected to the vertical magnet lever 14, which latter connection is I yielding, and constructed as follows:

At one side of vertical magnet lever 14 is an outwardly projecting pin 77, which en'- gages in the slotted end of rod 76, Figs. 24, 25 and 28, and at the o posite side of magnet lever 14 from pin 7% is an arm 78, Fig. 28, to which one end of a fiat spring is attached, the cuter end of the spring being in engagement with the rod 76' the has been revolved one or more steps, then outer end of the slot thereof, Figs. 24- and 28, so that the movement of vertical magnet lever 14 is yieldingly imparted to red 76, armature arm 71 and armature 69 through spring 80.

Now, since, if not prevented, the above described connection of armature arm 71 with vertical magnet lever 14 would cause a release of the engagement of arm 44 with the upper end of armature arm 71, every time main switch shaft 2 is lifted one step, it is prevented primarily by a pin 81, F1 s. 24, 26 and 27 which projects downwar y from ratchet wheel 9, and is in contact with a projection 82 on cross arm 44 in any vertical position of shaft 2, before it has been rotated one step, and, thereby the auxiliary switch'arms 26, 27, 28, 29 and 30, are held in the normal or out position shown in Fig. 10, at all times, when the vertical movements of shaft 2 are being made. If, however, shaft 2, is revolved one ste as seen in Fig. 27, at any of its severa vertical positions, on account of the armature arm (1 having no connection with the rotary movement mechanism, but only with the vertical movement lever 14, the cross lever 44, which controls the auxiliary switches, is not disturbed, but serves to hold the auxiliary switch arms in the initial position, as in Fig. 10 If, however, after shaft 2 vertical magnet 12 is energized, and if there is no current passing through magnet 48, to attract armature 69, the movement of lever 14, through rod 76, causes armature arm 71 to move from .the osition shown in Fig. 24 to the position sown in Fig. 25,

and disengage the outer end of cross lever 44 from the hook of spring 70, Fig. 25; and

. when vertical magnet 12 is tie-energized,

and vertical lever 14 and armature arm 71 fall back to the initial position, Fig. 24,

the end of cross lever 44 will contact spring 70 beyond the hookshoulder thereof and by virture of spring 38 on shaft 32,'move out of engagement with the hook, to the position shown in Fig. 27 when the auxiliary switch arms will assume the inward or second position shown inFig. 11.

If, however, in the connectors, as will be hereinafter. explained, an electric current should be passing through magnet 48, armature69 would be held down as in Fig. 24, and, although, vertical lever 14 may have a movement, it will not be transmitted to armature arm 71 for the reason that, spring 80 at the end of rod 7 6 is not of sufiicient strength to overcome the attraction of magnet 48, and the auxiliary switches named will not be changed from the initial position shown in Fig. 10, to the moved position in Fig. 11, .until the current is cut out of magnet 48.

In both the selectors and connectors,

outer end, Figs. 5 and 6, and this bent portion is disposed so as to be in contact with the outer surface of pawl 15 of vertical lever 14 to hold the pawl out of engagement with cylindrical ratchet 13, when lever 14 is in the initial position shown in Figs. 2 and 3, and is for the purpose as follows:

First, pawl 15 must be released from ratchet 13 after every step, in order that main switch shaft 2 may be moved not only in a step by step rotary direction, but also be adapted to be released and fall in the direction opposite to that induced by the action of pawl 15, when necessary, and then, it must be understood that vertical magnet lever 14, on account of serving to release cross arm 44, is fitted to have a greater movement than is necessary to move main switch shaft 2 one step, the first part of the movement being adapted to'operate rod 76 sufficiently to release cross arm 44 from the hook at the outer end of spring 70, and only a part of the terminal portion of the movement serving to operate pawl 15 so that the release arm 83 permits pawl 15 to engage the teeth of ratchet 13 only at the terminal portion of its movement, and this portion of the movement is limited an inclined faced stop 84 projecting from the top of frame 1 and against which face the for- Ward end portion of the pawl contacts with vertical armature arm 14 is adapted by its initial movement to operate rod 76 and lift magnet armature 69 if magnet 48, Fig. 24, is not energized.

In operating this system of telephone exchange it must be particularly understood that the source of electric current for operating the vertical, rotary, release, and auxiliary switch magnets, and for ringing the signal bells, is supplied at the central station, and for the talking circuit is supplied by a local transmitter circuit, not shown. in the usual manner. In order to more fully understand what is shown in the diagranr matic views-33, 34, 35, 36, 37 and ll-7, we will refer particularly to igs. 29 to 32, inclusive, in which is shown on a larger scale than in Fig. 34, means for producing an electric current, and for interrupting a portion of such current for operating therotary magnets 8, of all the selector switches and ringing the signal bells at the subscribers stations, and which means consists of a bat-; tery 65 having, in this instance, an elec-- mounted on insulated metal sleeve 90,- and 89 on sleeve 91.

In each of the commutators, one half of the peripheral surface consists of electric conducting material connected with the metal sleeves, and the other half is of insu-' lating materal, as indicated in Fig. 30.

Sleeve brush 92 connects sleeve 90 with wire 106 .fr0m the grounded side of battery 65, while brushes 93, 94 and 95, respectively connect with wires 96, 97 and 98, of which, wires 96 and 97 are inthe ringing or signal circuit, and, for this reason, commutators 86 and 87 are, relatively mounted on sleeve 90, so as to alternately make and break the current over the signal Wires 96 and 97. r

Brush 95 connects with wire 98, which leads to'the secondary of induction coil 99, and thence to main side of battery through wire 100. a

Sleeve brush 101 connects through wire 102 to wire 100, and commutator brush 103 connects to wire 104, which leads to the rotary magnets 8.

At 105 is an incandescent lamp serving as. a resistance in what we term the private wire .108, from main side of battery, and leading to the auxiliary magnets 48.

' The auxiliary switch arms of the selectors, such as 26 to 30, inclusive, Figs. 3, 33 and 34, are permanently connected as follows:

Switch arm 26 to relay 75 and rotary line wire 109; 27 to relay 74 and vertical line wire 110; 28 to wire 106 of grounded side of battery 65; 29 to private switch wiper 3 of bank 6 and arm 30 to wire 100 of 'main side of battery 65. i

In the initial position in both the selectors and connectors these auxiliary switch arms are engaged with contact points 33, -34, 35, 36 and 37, of which, contact point 33 of thefirst-selector, section B, Fig. 33, is connected to wire 100 of main side of battery through one retardation magnet 73 by wire 111, which wire is also connected to a normal wire 157 of the calling subscriber;

contact point 34 is connected to wire 100 of main side of battery by wire 113, through another retardation coil 72 and wire 113 is also connected with normal wire 156 of the calling subscriber; contact point 35 1s connected to the middle spring 112, between relays 74 and 75 contact 36 to the auxlliary switch electromagnet 48; and 37 s connected to the vertical motor magnet 12.

After the auxiliary switch has been operated from the initial position shown in Fig. 10, to that shown in Fig. 11, the switch arms 26 to 30 are in connection with contact points 39 to 43 as follows:

Contact point 39 is connected to rotary switch arm 5 of bank 7, Fig. 1, and contact 40 with vertical switch arm 4 of bank 7; 41 has no connection or is a blank; 42 with grounded side of battery 65 through wire 106, and contact 43 has no connection.

The connections of the auxiliary switch arms and contact points thereof of the second selector'switch, Fig. 33, section C, are

the same as is shown in section B, with the The connections of the auxiliary switch arms and contacts thereof of, the selectors,

' exception of the normal wires 156 and 157.

having been indicated, as'above, we will now indicate the connections of the auxiliary 1 switch arms of the connectors and contacts wiper 3 of bank 6, and arm 30 to wire 100 i I from main side of battery 65.

The auxiliary switch arms of the connectors are connected in the initial position,

Fig. 10, as in the selectors, with contact 33,.

3'4, 35, 36 n 7- l Contact point 33 of theconnectors is connected to wire .107 through a resistance 118 and then to the primary side of an induction coil 99, while contact .34 is connected to wire 100 from the mainside of battery 65 through resistance 119, only; 35 connects to wire 106 from the grounded side of battery 65; 36 to the auxiliary switch controlling magnet 48; and contact '37 to the rotary motor magnet 8.

- After the auxiliary switch of the connector has been operated to the moved position shown in Fig. 1.1, the switch arms 26 to 30 are in connection with contacts 39 to 43,

and contact 39 v connects with battery 65 and Wire 1100' through one retardation. coil 73, while contact 40 connects to wire 100 through another retardation coil 72; 41 connects to wire 106 through a special coil 120, termedp the ringing relay coil, which is for the purpose of throwing an alternating current out on a subscribers line as a call signal; while contact point42 connects to wire 106 from grounded side of battery. and contact 43 is first selectors the contacts 33 and 34 also make connection with two wires 114 and 115, termed the normal or individual interconnecting wires of the called subscriber, as shown in Figs. 33 and 34.

In describing the operation of the first selectors, illustrated in Figs. 1 to 19, inclu sive, from the normal position, for convenience of description, we termmagnets 8, 12 and 53, respectively, the rotary, vertical and release magnets, since they serve to move shaft 2 in a rotary and vertical direction, and to release the same, so that it may return bythe action of gravity and spring 16, to the initial position.

In setting the main switch arms 3, 4 and 5, to any particular contact points in banks 6 and 7 from the initialposition shown in Figs. 1 and 2, vertical magnet 12 is first 9 enen' gi ed whem main switch shaft 2 with mam sw tch arms 3, 4 and 5 are lifted by pawl 15 through the pitch of one of the teeth of cylinder ratchet 13, when, although pin 18 at the to of shaft 2 will stillbe held against pin 19, y virtue of spring 16, at the lower end of the shaft, the latter will be lifted above the short pin 20, Fig. 16, so that the shaft may be rotated step by step in one direction.

During the time shaft 2 is being lifted one step, several other important moves have been made, the first of which is that the endof release lock spring 56 has been lifted clear of projection 58'of double detent 21,

22, Fig. 16, by the action of hook 59 of.

vertical magnet lever 14, when under pressure of detent spring 23, the release detents 21 and 22 are together brought into engagement' with rhtchets 9 and 13 of shaft 2, as 40 seen in Fig. 8, then as soon as vertical magnet 12 is de-energized, magnet lever 14 falls back to the initial position, when the release lock spring 56 rests upon the end of projection 58 of double detent 21-22 as seen in Fig. 17. r

The parts of the selector or connector are now in such a position that the main switch arms 3, 4 and 5 will be in register with the first or lower rows of contact points of banks 6 and 7, and the other parts of the switch. not be changed in position if it should be necessary to lift shaft 2, step'by step, so that the main switch arms 3, 4 and 5, thereof register with some higher row of'con'tact. points, this may be accomplished by successively electrically energizing and de-energizing vertical magnet 12. 'When the desired. concave row of contact points has been found, the first contact 60 points in the rows will be engaged by the switch arms of shaft 2, by energizing rotary electromagnet 8 once, during which time pawl 11 of lever 10 engages ratchet 9, which is turned the pitch of one tooth and is held 65 by detent 22 in such moved posit-ion as shown in Fig. 9. In the meantime, the outer end of an arm 60 connected with the armature of rotary magnet 8, contacts the armature 47 of magnet 48, which is moved from the open or normal position shown in Figs. 2, 10 and 12, to the closed position shown in Figs. 11 and 13.

Normally, in the selectors, the outer end of arm 44 is held, as shown in Figs. 2, 10 and 12, against shoulder 45 at the top of spring arm 46 of armature 47, but when this armature is depressed tothe closed position the stiff arm is moved from back stop pin 61 to the position shown in Fi .13,when arm 44, now being movable lateral l slides off of .shoulder 45 of spring arm 46, and under pressure of spring 38 on shaft 32 the arm moves outwardly to shoulder 49 of stifi arm 50, and if there should be nocurrent through magnet 48 to hold armature 47 in contact, and thereby close the circuit through rotary magnet 8, the arm 50 would fall back to pin 61, Fig. 14, when the cross arm 44, would move out to the position shown in Fig. 15, and the arms 26 to 30, inclusive, of the auxiliary switch, move from outer contacts 33 to 37, inclusive, to inner contacts'39 to 43 inclusive.

henever the armature of rotary magnet 8 is operated, the action of the arm connected thereto serves to close armature 47 of magnet 48, and by pressure of insulated pin 64 cause insulated switch springs 62 and 63,Fig. 13, to contact at their top ends and close a circuit, so that a current, if there be any, would pass through these springs.

In calling a distant subscriber by this sys tern, if the first contact point in some particular row of the first selector is not engaged or busy, the action of the rotary ,magnet 8 would be as follows:

. \Vhe'n rotary magnet 8 is de-energized,

and armature 47 is permitted to lift by removal of the contact of arm 60 through the resiliency of switch springs 62 and 63 acting on arm 50, the latter. falls back to stop pin 61, and releasing itself from arm 44, which at thefinstant of the release appears in Fig.14, the pressure of spring 38 on shaft 32 causes arm 44 to be instantly moved to the position shown in Fig. 15, or as more plainly shown in Fig. 11, where the switch arm 30 is shown connected to contact point 43'of the inner row, instead of the outer row,

. as shown in the initial position in Fig. 10. If, however, the first contact points in the desired row be engaged or busy the action of the rotary magnet 8 and the private magnet 48 is as follows:

When main switch arm 3, engages the first contact point in the desired row of bank 6, Fig. 1, or more clearly shown in section-B, Fig. 35, magnet 48 is energized by current from battery 65 through wire 106, main switch arm 66 of bank 67 interconnecting wire to arm 3 of bank 6, thence to magnet 48 and by wire 100 to battery and so long as magnet 48 is energized, the springs 62 and 63 of private magnet 48-are held in contact, and close the circuit through rotary magnet 8, battery 65 and commu-' tator 89, andtat each revolution of commutator 89 the local circuit from battery 65, of which it forms a part, is opened and closed, and at each closing oi the circuit, rotary magnet .8 is energized and-in the opening of the circuit is de-energize'd, causing mainswitch arm- 3 to move, step by step, until it engages a vacant contact point, when magnet 48 is de-energized, causing springs 62 and 63 to separate and open the local circuit through rotary'magnet 8.

As .the arms 4'and 5 which are seeking to make atalk-ing circuit areconnectedto the shaft 2 and move in unison with the arm 3 it is evident that as soon as arm 31has made a contact with an open or not-busy? linearms 4 and-5 will also have made connection with a contact point through which the talking circuitis established.

lg. 36, section B, is a duplicate of Fig. 35, sectionB, except that main switch arm 3 -,is in engagement with the second contact point of an interconnecting line which is also busy, and Fig. 37, section B, shows the first selector main switch arm 3 in engagement with the third .contact point-connected with an interconnecting line not'busy.

- The action of main switch shaft 2 of the second selector to find the proper contact point is the same asdescribed for the first selector.

As stated hereinbefore, the operative parts of the connectors are the same-as in the'first and second selectors, with the exception that,

. the mechanism controlling armature 47 of private magnet 48 is adapted to normally hold the armature closed, as is seen in Fig. 24,-by the action of spring 70 against armature arm 71-, and the step by step rotary movement of shaft 2 in the connector is made by means of the calling key, or other mechanism at the calling subscribers telephone or station until the desired contact point in the row is found, without any further change in the position of the parts of the switch, which is now set to some particularsubscribers number, and serves as a medium of telephonic communication, as is hereinafter described.

After communication is ended, the opera tion of release or the returning of the mainswitch arms 3, 4 and 5, and the other parts,

1 back to the initial position, is accomplished by energizing release magnet 53, when the armature release [lock spring 56 is moved from'the position shown in Fig. 8, to the'position shown in Fig. 6,. by the closing of armature .54, when the hole 57 in the end of spring 56 will be engaged by the projection 58 of double detent 21-2 2,-as shown in Fi 6. if new release magnet 53 is de-energized,

the strong release spring 55 will drawthe armature to the open or initial position, and with it the release lock spring 56, and double p'awls 21-22 which are from their ratchets and leaves shaft 2 free so that it will first-revolve by the act-ion of spring16 back to the position when the sta-- tionary detent is in groove 25 of ratchet 13,

and stop-pin :18 against pin 19, when it will .drop by gravity to the initial position, .as in count of the cross rod 51, Figs. 7, 8 and 9, having one end in contact with the arm 52 of double detent 2122,- the disengaging thus disengaged.

Figs. 1, 2 and 3. In the meantime, on acmovementof the double detent when cross I arm rod 51 is in the position shown in Fig. 9, will cause arm 52 of the double detent, through cross rod 51, andshort arm 32, to partially revolve shaft 32 against the tension of spring 38, and move the switch arms attached to arm 31 from the inner position shown in Figv 11, to the outer or initial po-' spring arm shoulder 45 serves as a catch to hold arm 44 in the initial position, and all the power for accomplishing the release, as described, arises from the resiliency of spring 55, after being bent by the action of release magnet 53.

At the top end of all the selectors and connectors in this instance, are four single spool magnets, arranged in pairs as seen in Figs. 1, 2, 3 and 4, and each of these magnets is provided with a separate armature, and to each of which is connected anal'm for operating a spring switch, the same, to-

gether with their switches, being shown on a large scale in Figs. 20 to 23, inclusive.

Two of the magnets, 72 and 73, Fig. 4, serve also as retardation coils.

Two of the magnets 74 and 75'are wound to serve as relays whose coils are in communication with the subscribers but whose armatures are adapted to operate a switch for supplying electric current from a source local at the central exchange, for operating all the motor magnets.

When current is sent through the vertical line wire 110 from a s'ubscribers station,

relay magnets 74 in both the selectors and connectors operate toclose the central station local circuit between spring 137 and center spring 112, Fig. 20, and the retardation magnets 72, Fig. 23, operate to close 

